Recently, with the multimediatization of information in mobile communication systems as represented by mobile phones or the like, it is becoming popular to transmit not only audio data, but also large amounts of still picture data, motion picture data and the like. To realize the transmission of large amounts of data, an approach is being broadly investigated according to which a high-frequency radio band is used to obtain a high-transmission rate.
However, in the case of using a high-frequency radio band, while a high transmission rate can be expected at a short distance, attenuation due to transmission distance is significant. For this reason, in the case of expanding this to a real system, for instance, the coverage area of a base station becomes small, which requires that a larger number of base stations to be provided. Since the set-up of base stations involves large costs, a technology is strongly required for realizing communication services while suppressing an increase in the number of base stations.
As a conventional technology related to this, there exists the technology described in Patent Document 1, for example. In the conventional technology of this Patent Document 1, a communication network of cellular-dedicated radio channels which are formed between a base station and a mobile station, and an ad-hoc network formed between mobile stations are both used to combine signals, whereby an improvement of the diversity effect is obtained.
1 Patent Document 1: Japanese Patent Application Laid-Open No. 2001-189971